priority_queue<pair<int, int>, vector<pair<int, int>>, mycomparison> pri_que;
时间: 2024-05-04 11:13:05 浏览: 18
priority_queue是C++标准库中的一个容器适配器,它提供了一种基于优先级的元素访问方式。在priority_queue中,元素按照一定的优先级进行排序,并且每次访问时都会返回优先级最高的元素。
在你提供的代码中,priority_queue的定义如下:
```cpp
priority_queue<pair<int, int>, vector<pair<int, int>>, mycomparison> pri_que;
```
这里的`pair<int, int>`表示priority_queue中存储的元素类型为`pair<int, int>`,即一个整数对。`vector<pair<int, int>>`表示底层容器使用vector来存储元素。`mycomparison`是一个自定义的比较函数对象,用于确定元素的优先级。
关于自定义比较函数对象,它需要满足严格弱序关系,即对于任意两个元素a和b,比较函数对象返回true表示a应该排在b之前。在这个例子中,`mycomparison`可能是一个自定义的结构体或类,重载了函数调用运算符`operator()`,用于比较两个pair<int, int>类型的元素。
总结一下,你提供的代码定义了一个存储pair<int, int>类型元素的priority_queue,底层容器为vector,并使用自定义的比较函数对象mycomparison来确定元素的优先级。
相关问题
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq
This is a declaration of a priority queue in C++ that stores pairs of integers. The priority queue is implemented using a min-heap, which means that the smallest element will have the highest priority. The first integer in the pair is the priority and the second integer is the value.
The syntax for declaring a priority queue in C++ is:
priority_queue<data_type, container_type, comparison_function>
In this case, the data type is a pair of integers (pair<int, int>), the container type is a vector (vector<pair<int, int>>), and the comparison function is the default less-than operator (>).
However, in order to implement a min-heap, we need to use the greater-than operator (<) instead. So we pass greater<pair<int, int>> as the comparison function.
Overall, this priority queue will store pairs of integers in ascending order of their first element. If two pairs have the same first element, then they will be ordered based on their second element in ascending order as well.
priority_queue<int,vector<int>,greater<int> > q2
以下是关于priority_queue的介绍和演示:
1. 介绍:
priority_queue是C++ STL中的一个容器适配器,它提供了常数时间的最大元素访问能力,并且在对数时间内插入和删除元素。默认情况下,priority_queue是一个最大堆,即最大元素总是位于队列的开头。通过指定greater<int>作为第三个模板参数,可以创建一个最小堆,使得最小元素位于队列的开头。
2. 演示:
```cpp
#include <iostream>
#include <queue>
using namespace std;
int main() {
int a[] = {3, 1, 4, 1, 5, 9};
int len = 6;
priority_queue<int, vector<int>, greater<int> > qi2; // 创建一个从小到大的优先级队列
for (int i = 0; i < len; i++) {
qi2.push(a[i]);
}
while (!qi2.empty()) {
cout << qi2.top() << " "; // 从小到大输出队列中的元素
qi2.pop();
}
cout << endl;
return 0;
}
```
运行以上代码,将输出:1 1 3 4 5 9